1. Field of the Invention
The present invention relates to a control device for an internal combustion engine.
2. Related Art
There is known an internal combustion engine in which a target intake air amount is calculated, a target throttle opening required for making the actual intake air amount equal to the target intake air amount is calculated, and the throttle valve is driven by an actuator so that the actual throttle opening is made equal to the target throttle opening (see Japanese Unexamined Patent Publication No. 5-65845).
When the engine is accelerated and thus the target intake air amount is increased stepwise, for example, the target throttle opening and, accordingly, the actual throttle opening increases suddenly and then decreases suddenly, after which it converges to a certain value, in order to quickly make the actual intake air amount equal to the target value. In other words, when the target intake air amount is increased or reduced, the throttle opening fluctuates or oscillates widely.
On the other hand, while the target intake air amount continuously increases or decreases when the engine is accelerated or decelerated, it increases and decreases alternately and repeatedly when the engine steady operation is in process. The above-mentioned fluctuation in the throttle opening will occur even when the target intake air amount is slightly increased or reduced. Accordingly, when the engine steady operation is in process, there may by a case in which the throttle opening fluctuates with a large amplitude. In addition, the durability of the throttle valve or the actuator may be deteriorated in a short time of period.